1. Field of the Invention
The present invention relates to an apparatus for placing a carriage on a track comprising two rails, each rail having a rail head, the carriage having a flanged wheel associated with each rail and being linked to a frame of a track working machine mounted for mobility on the track, and drive means linking the carriage to the track working machine frame for displacing the carriage between an inoperative and an operating position, the apparatus comprising a rail sensing element mounted on the carriage for sensing a respective one of the rails.
2. Description of the Prior Art
German patent application No. 2,927,729, published Feb. 21, 1980, discloses an apparatus for placing a carriage on, i.e. guiding it onto, a track, the carriage being linked to a frame of a track working machine by a vertical displacement drive. The carriage is automatically centered by a guide with respect to the center of the track in its raised, inoperative position. The apparatus is linked to the track working machine frame independently of the carriage and is comprised essentially of a pair of levers acting as rail sensing elements. A carrier frame for the pair of levers is linked to the machine frame and the levers are so mounted on the carrier frame that they are pivotal in a vertical plane extending transversely to the track. The pivoting axes of the levers are horizontally spaced a distance corresponding substantially to the track gage. The rail sensing levers are coupled to each other by a synchronization rod so that pivoting of one lever by a pivoting drive causes a mirrorimage movement of the other lever. The levers have free ends acting as rail sensing abutments for engagement with the gage sides of the rail heads. In the rest position of the apparatus, the rail sensing levers are pivoted up towards the center of the track. In the operative position, the pivoting drive is actuated and the levers are synchronously spread apart into engagement with the gage sides of the rail heads. If the apparatus is not accurately centered with respect to the track center, for example when the track working machine travels in a track curve, one lever will necessarily engage the rail head of the associated rail before the other lever does. As the levers are spread further, the carrier frame of the pair of levers is displaced towards the track center until the other lever, too, engages the rail head of the rail associated therewith, and the apparatus is thus accurately centered on the track. In this centered position, the carrier frame of the placing apparatus serves to guide the carriage into a position centered with respect to the track center as it is lowered onto the track. For this purpose, finger-shaped aligning supports are affixed to the carriage, which are deflected by guide ramps affixed to the carrier frame of the placing apparatus until the flanged wheels of the carriage engage the associated rails, i.e. the carriage is guided onto the track and is centered with respect thereto. This apparatus is structurally relatively complicated and may function improperly in superelevated track curves.
U.S. Pat. Nos. 3,808,693, dated May 7, 1974, No. 4,391,134, dated July 5, 1983, and No. 4,691,565, dated Sept. 8, 1987, disclose track measuring and surveying machines with various hydraulically operated and controlled transverse displacement drives for rail sensing elements, including devices for emitting warning signals.